1. Field of the Invention
The present invention relates to a honeycomb structure, and more particularly, it relates to a honeycomb structure which is a catalyst carrier and also functions as a heater when a voltage is applied thereto and which has an excellent heat shock resistance.
2. Description of Related Art
Heretofore, a honeycomb structure made of cordierite, onto which a catalyst is loaded, has been used in treatment of harmful substances in an exhaust gas discharged from a car engine. Moreover, it is known that a honeycomb structure formed by a sintered silicon carbide body has been used in purification of the exhaust gas. Here, when the exhaust gas is treated by the catalyst loaded onto the honeycomb structure, a temperature of the catalyst needs to be raised up to a predetermined temperature. However, the catalyst temperature is low at the start of the engine, which has caused the problem that the exhaust gas is not sufficiently purified.
To solve the problem, it has been disclosed that a honeycomb structure made of a conductive ceramic material and having both ends provided with electrodes is used as a catalyst carrier with a heater (e.g., see Patent Document 1). Moreover, it has been disclosed that a honeycomb heater constituted of a conductive honeycomb structure having a large number of through holes and two energizing means arranged on a side surface of this honeycomb structure is used as the catalyst carrier (e.g., see Patent Document 2).